Separator Electrolyte Wettability Adhesion Phase Separation
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Solution Overview
Problem
Current separators for electrochemical elements, particularly lithium secondary batteries, face challenges with insufficient electrolyte wettability and adhesion to electrodes, which affect activation time and battery lifetime.
Innovation Solution
A separator comprising a porous polymer substrate with a layer formed from a binder polymer solution containing a first and second binder polymer, along with inorganic particles, is developed. The binder polymers are applied with specific concentrations and ratios, and the solution is phase-separated under controlled humidity conditions to enhance adhesion and wettability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If the separator thickness is reduced for lightness and compactness, then the electrochemical element becomes lighter and more compact, but the mechanical strength of the separator is compromised
Solution Approach 1:
The patent employs composite materials by incorporating inorganic particles into the porous coating layer formed on the porous polymer substrate. The inorganic particles (such as alumina, silica, or titania) provide structural reinforcement and enhance mechanical strength, allowing the separator to be made thinner without compromising integrity. The binder polymer matrix holds these particles together, creating a robust composite structure that maintains strength at reduced thickness.
Solution Approach 2:
The patent utilizes porous materials by forming a porous coating layer with controlled porosity on the porous polymer substrate. The porous structure provides mechanical strength through the network of pores and walls, allowing thinning of the separator while maintaining structural integrity. The porosity also facilitates electrolyte penetration and ion transport, balancing mechanical strength with functional performance in thin separator design.
2Strength
If binder polymer is distributed with gradient concentration to enhance adhesion between separator and electrode, then adhesion is improved, but electrolyte wettability of the porous polymer substrate does not increase
Solution Approach 1:
The patent applies local quality by creating a porous coating layer with optimized binder polymer concentration and composition on the surface of the porous polymer substrate. This coating layer is specifically designed to provide both adhesion to the electrode and enhanced electrolyte wettability. The binder polymer concentration and type are selected to achieve dual functionality: strong adhesion at the electrode interface and high electrolyte wettability at the exposed surface, resolving the trade-off between these two requirements.
Solution Approach 2:
The patent uses composite materials by combining inorganic particles with binder polymer in a porous coating layer. The inorganic particles contribute to electrolyte wettability through their hydrophilic surfaces, while the binder polymer provides adhesion to the electrode. This composite approach allows simultaneous optimization of both adhesion and wettability properties that cannot be achieved with binder polymer alone.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution significantly improves electrolyte wettability and adhesion to electrodes, reducing activation time and enhancing battery lifetime while maintaining mechanical strength and safety characteristics.
Implementation Method 1
the binder polymer is phase-separated under a certain humidity condition so that more binder polymer is distributed on a surface of the separator where the electrode is adhered
Implementation Method 2
a porous coating layer containing a mixture of an inorganic particle and a binder polymer is formed on at least one surface of the porous polymer substrate, because while the porous coating layer may enhance electrolyte wettability
Data Source
AI summary
The present invention relates to a separator for an electrochemical element having improved electrolyte wettability and an electrochemical element comprising the separator, in which a layer containing at least two binder polymers having different slopes on the frequency-storage modulus curve is formed on a surface of the separator, and with one of the binder polymers being concentratedly distributed on the surface of the separator, the separator and the electrode can be securely attached, and with the other binder polymer being permeated and coated onto a porous polymer substrate, electrolyte wettability can be enhanced.